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The CDL example and the associated text

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in docs/cdl.dox do not show and describe
how declare the type of an attribute.
So modified the example and text to
clarify. Also clarified how type inference
works for attributes whose value is a string.
This commit is contained in:
dmh 2014-10-27 16:24:22 -06:00
parent 13be04f699
commit 481b9ac8ee
1 changed files with 23 additions and 15 deletions
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38
docs/cdl.dox
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@ -23,12 +23,12 @@ data.
double p(time,lat,lon);
int rh(time,lat,lon);
lat:units = "degrees_north";
char lat:units = "degrees_north";
lon:units = "degrees_east";
time:units = "seconds";
z:units = "meters";
z:valid_range = 0., 5000.;
p:_FillValue = -9999.;
float z:valid_range = 0., 5000.;
double p:_FillValue = -9999.;
rh:_FillValue = -1;
data:
@ -75,18 +75,26 @@ type, a length, and a value. In contrast to variables that are
intended for data, attributes are intended for ancillary data or
metadata (data about data).
In CDL, an attribute is designated by a variable and attribute name,
separated by a colon (':'). It is possible to assign global attributes
to the netCDF dataset as a whole by omitting the variable name and
beginning the attribute name with a colon (':'). The data type of an
attribute in CDL, if not explicitly specified, is derived from the
type of the value assigned to it. The length of an attribute is the
number of data values or the number of characters in the character
string assigned to it. Multiple values are assigned to non-character
attributes by separating the values with commas (','). All values
assigned to an attribute must be of the same type. In the netCDF-4
enhanced model, attributes may be declared to be of user-defined type,
like variables.
In CDL, an attribute is designated by a data type, a
variable, and an attribute name. The variable and the
attribute name are separated by a colon (':'). If present,
the data type precedes the variable name. It is possible to
assign global attributes to the netCDF dataset as a whole by
omitting the variable name and beginning the attribute name
with a colon (':'). The data type of an attribute in CDL, if
not explicitly specified, is derived from the type of the
value assigned to it, with one exception. If the value is a
string, then the inferred type is char, not string. If it
is desired to have a string typed attribute, this must be
stated explicitly.
The length of an attribute is the number of data values or
the number of characters in the character string assigned to
it if the type is char. Multiple values are assigned to
non-character attributes by separating the values with
commas (','). All values assigned to an attribute must be of
the same type. In the netCDF-4 enhanced model, attributes
may be declared to be of user-defined type, like variables.
In CDL, just as for netCDF, the names of dimensions, variables and
attributes (and, in netCDF-4 files, groups, user-defined types,